Typically, an accelerator manipulation device is either a mechanical device or an electronic device. The mechanical accelerator pedal system includes a pedal that is pivotally mounted on the driver's side floorboard, a throttle mechanism installed in the intra-engine suction system, and a cable connecting the accelerator pedal to the throttle mechanism that transmits a manipulation force. An electronic accelerator pedal system includes an accelerator pedal pivotally mounted on the driver's side floorboard and a detection sensor installed on the accelerator pedal that detects the position of the accelerator pedal on a real time basis.
A conventional mechanical accelerator pedal system generates a foot pressure hysteresis effect, and thus, no special problem occurs in the foot pressure tuning of the accelerator pedal. The foot pressure hysteresis effect refers to a phenomenon where a driver's passive reaction force (about 2 kgf), caused from friction of the cable during the releasing of the pedal, is small compared to the driver's passive reaction force (about 3.5˜4.5 kgf) during the depressing of the pedal. In contrast, in a conventional electronic accelerator pedal system the driver's passive reaction force, during depression, steady state, and release of the pedal, is determined only by the inherent elasticity of a return spring. The quantitative degree of the reactive force of the return spring is determined on the basis of depression of the pedal for acceleration. However, a drawback of this system is that there is no resistance in the system which counteracts the spring's reactive force while a driver holds a steady accelerator position. As a result, the driver's ankle is subjected to fatigue after repetitive depressions of the pedal. Consequently, the manipulability of the accelerator is aggravated.